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Abstract:

Certain embodiments of the invention may include systems, methods, and
apparatus for modifying a turbine casing. According to an example
embodiment of the invention, a method is provided for modifying a turbine
casing. The method can include providing one or more casing retention pin
bores in the turbine casing; inserting a retention pin in the one or more
casing retention pin bores; providing one or more patch ring segments
configured to be radially constrained by at least a portion of the
turbine casing and further configured to slide circumferentially in
cooperation with at least a portion of the turbine casing, wherein the
one or more patch ring segments comprise at least one retention pin
locking bore; installing the one or more patch ring segments in the
turbine casing to radially constrain the one or more patch ring segments;
and engaging the retention pin in the at least one retention pin locking
bore to circumferentially constrain the one or more patch ring segments
to the turbine casing.

Claims:

1. A method for modifying a turbine casing, the method comprising:
providing one or more casing retention pin bores in the turbine casing;
inserting a retention pin in the one or more casing retention pin bores;
providing one or more patch ring segments configured to be radially
constrained by at least a portion of the turbine casing and further
configured to slide circumferentially in cooperation with at least a
portion of the turbine casing, wherein the one or more patch ring
segments comprise at least one retention pin locking bore; installing the
one or more patch ring segments in the turbine casing to radially
constrain the one or more patch ring segments; and engaging the retention
pin in the at least one retention pin locking bore to circumferentially
constrain the one or more patch ring segments to the turbine casing.

2. The method of claim 1, wherein engaging the retention pin in the at
least one retention pin locking bore comprises engaging at least a
portion of the retention pin in at least one of the one or more casing
retention pin bores, and further engaging at least a portion of the
retention pin in the at least one retention pin locking bore when the one
or more casing retention pin bores are circumferentially aligned with the
at least one retention pin locking bore.

3. The method of claim 1, further comprising inserting a spring in the
one or more casing retention pin bores, wherein the spring provides force
for engaging the retention pin in the at least one retention pin locking
bore.

4. The method of claim 1, wherein providing one or more casing retention
pin bores in the turbine casing comprises providing one or more radial
bores in the turbine casing.

5. The method of claim 1, wherein installing the one or more patch ring
segments in the turbine casing comprises installing the one or more patch
ring segments in a flow path stage associated with the turbine.

6. The method of claim 1, wherein providing one or more patch ring
segments further comprises providing a guide slot in the one or more
patch ring segments for guiding the retention pin into the at least one
retention pin locking bore.

7. The method of claim 1, wherein providing one or more patch ring
segments further comprises providing a retention pin refraction bore for
disengaging the retention pin from the least one retention pin locking
bore, wherein the retention pin retraction bore comprises a diameter
smaller than the diameter of the retention pin.

8. A system comprising: a gas turbine comprising a flow path stage
casing; an assembly for repairing the casing, the assembly comprising:
one or more casing retention pin bores in the casing; a retention pin in
the one or more casing retention pin bores; one or more patch ring
segments configured to be radially constrained by at least a portion of
the casing and further configured to slide circumferentially during
assembly or disassembly in cooperation with at least a portion of the
turbine casing, wherein the one or more patch ring segments comprise at
least one retention pin locking bore, and wherein the retention pin
engages with the at least one retention pin locking bore to
circumferentially constrain the one or more patch ring segments to the
casing.

9. The system of claim 8, wherein the retention pin is operable to engage
with at least a portion of one of the one or more casing retention pin
bores, and wherein the retention pin is further operable to engage with
at least a portion of the at least one retention pin locking bore when
the one or more casing retention pin bores are circumferentially aligned
with the at least one retention pin locking bore.

10. The system of claim 8, further comprising a spring positioned in the
one or more casing retention pin bores, wherein the spring provides force
for engaging the retention pin in the at least one retention pin locking
bore.

11. The system of claim 8, wherein the one or more casing retention pin
bores comprises radial bores in the casing.

12. The system of claim 8, wherein the one or more patch ring segments
further comprises a guide slot for guiding the retention pin into the at
least one retention pin locking bore.

13. The system of claim 8, the one or more patch ring segments further
comprise a retention pin retraction bore for disengaging the retention
pin from the least one retention pin locking bore, wherein the retention
pin retraction bore comprises a diameter smaller than the diameter of the
retention pin.

14. An apparatus comprising: an assembly for repairing a casing
associated with a gas turbine flow path stage, the assembly comprising:
one or more casing retention pin bores in the casing; a retention pin in
the one or more casing retention pin bores; and one or more patch ring
segments configured to be radially constrained by at least a portion of
the casing and further configured to slide circumferentially during
assembly or disassembly in cooperation with at least a portion of the
turbine casing, wherein the one or more patch ring segments comprise at
least one retention pin locking bore, and wherein the retention pin
engages with the at least one retention pin locking bore to
circumferentially constrain the one or more patch ring segments to the
casing.

15. The assembly of claim 14, wherein the retention pin is operable to
engage with at least a portion of one of the one or more casing retention
pin bores, and wherein the retention pin is further operable to engage
with at least a portion of the at least one retention pin locking bore
when the one or more casing retention pin bores are circumferentially
aligned with the at least one retention pin locking bore.

16. The assembly of claim 14, further comprising a spring positioned in
the one or more casing retention pin bores, wherein the spring provides
force for engaging the retention pin in the at least one retention pin
locking bore.

17. The assembly of claim 14, wherein the one or more casing retention
pin bores comprises radial bores in the casing.

18. The assembly of claim 14, wherein the one or more patch ring segments
further comprises a guide slot for guiding the retention pin into the at
least one retention pin locking bore.

19. The assembly of claim 14, the one or more patch ring segments further
comprise a retention pin refraction bore for disengaging the retention
pin from the least one retention pin locking bore, wherein the retention
pin retraction bore comprises a diameter smaller than the diameter of the
retention pin.

20. The assembly of claim 14, further comprising a retraction tool having
an outer diameter smaller than an inner diameter of the retention pin
retraction bore and operable to retract the retention pin for
disassembly.

Description:

FIELD OF THE INVENTION

[0001] This invention generally relates to turbines and in particular to
modifying a turbine casing.

BACKGROUND OF THE INVENTION

[0002] Blades or "buckets" are utilized in turbines for conversion of
energy. The buckets are typically attached by one end to a rotor, while
the opposite ends extend nearly to a circumferential casing associated
with the turbine. A gap between the bucket ends and the casing is usually
made as small as possible to minimize flow around the blade ends. During
the operation of the turbine, certain conditions can arise that may cause
the blade ends to scrape against the casing and damage the casing
surface, and as a result, repairs are sometimes required. It is a common
practice to repair a damaged turbine casing using patch ring segments or
shims. Such materials can be attached to the inner diameter of the casing
to repair the damaged casing surface. The patch ring segments can be
secured with screws, but there is always a risk that a displaced screw
may fall into the flow path and damage other components.

BRIEF SUMMARY OF THE INVENTION

[0003] Some or all of the above needs may be addressed by certain
embodiments of the invention. Certain embodiments of the invention may
include systems, methods, and apparatus for modifying a turbine casing

[0004] According to an example embodiment of the invention, a method is
provided for modifying a turbine casing. The method can include providing
one or more casing retention pin bores in the turbine casing; inserting a
retention pin in the one or more casing retention pin bores; providing
one or more patch ring segments configured to be radially constrained by
at least a portion of the turbine casing and further configured to slide
circumferentially in cooperation with at least a portion of the turbine
casing, wherein the one or more patch ring segments comprise at least one
retention pin locking bore; installing the one or more patch ring
segments in the turbine casing to radially constrain the one or more
patch ring segments; and engaging the retention pin in the at least one
retention pin locking bore to circumferentially constrain the one or more
patch ring segments to the turbine casing.

[0005] According to another example embodiment of the invention, a system
is provided. The system can include a gas turbine which may include a
flow path stage casing. The system can include an assembly for repairing
the casing. The assembly can include one or more casing retention pin
bores in the casing; a retention pin in the one or more casing retention
pin bores; one or more patch ring segments configured to be radially
constrained by at least a portion of the casing and further configured to
slide circumferentially during assembly or disassembly in cooperation
with at least a portion of the turbine casing, wherein the one or more
patch ring segments include at least one retention pin locking bore, and
wherein the retention pin engages with the at least one retention pin
locking bore to circumferentially constrain the one or more patch ring
segments to the casing.

[0006] According to another example embodiment of the invention, an
apparatus is provided. The apparatus can include an assembly for
repairing a casing associated with a gas turbine flow path stage. The
assembly can include one or more casing retention pin bores in the
casing; a retention pin in the one or more casing retention pin bores;
and one or more patch ring segments configured to be radially constrained
by at least a portion of the casing and further configured to slide
circumferentially during assembly or disassembly in cooperation with at
least a portion of the turbine casing, wherein the one or more patch ring
segments comprise at least one retention pin locking bore, and wherein
the retention pin engages with the at least one retention pin locking
bore to circumferentially constrain the one or more patch ring segments
to the casing.

[0007] Other embodiments, features, and aspects of the invention are
described in detail herein and are considered a part of the claimed
inventions. Other embodiments, features, and aspects can be understood
with reference to the following detailed description, accompanying
drawings, and claims.

BRIEF DESCRIPTION OF THE FIGURES

[0008] Reference will now be made to the accompanying drawings, which are
not necessarily drawn to scale, and wherein:

[0009]FIG. 1 is a diagram of an illustrative turbine according to an
example embodiment of the invention.

[0010]FIG. 2 is a diagram of a illustrative flow path stages of a turbine
according to an example embodiment of the invention.

[0011]FIG. 3 is a perspective view diagram of an illustrative patch ring
according to an example embodiment of the invention.

[0012]FIG. 4 is a diagram of an illustrative patch ring assembly
according to an example embodiment of the invention.

[0013]FIG. 5 is a diagram of an illustrative patch ring assembly with an
engaged retention pin according to an example embodiment of the
invention.

[0014]FIG. 6 is a diagram of an illustrative patch ring assembly with pin
retraction tool according to an example embodiment of the invention.

[0015]FIG. 7 is a flow diagram of an example method according to an
example embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Embodiments of the invention will be described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may, however, be
embodied in many different forms and should not be construed as limited
to the embodiments set forth herein; rather, these embodiments are
provided so that this disclosure will be thorough and complete, and will
fully convey the scope of the invention to those skilled in the art. Like
numbers refer to like elements throughout.

[0017] Certain example embodiments of the invention may enable attaching
and securing the patch ring segments to the turbine casing. According to
certain example embodiments, gas turbines casings may be repaired with
patch rings when the flow path on the casing is damaged due to rubs or
failure of rotor blades. According to example embodiments, grooves or
slots may be made on the damaged flow path, and patch rings may slide
into the grooves or slots to build the casing back to the desired casing
dimension.

[0018] From a practical standpoint, it can be very difficult to slide a
patch ring into casing grooves or slots when the patch ring is comprised
of only a few segments. Therefore, according to an example embodiment of
the invention, the patch rings can be made in 6-12 segments for ease of
assembly. After assembly, the patch ring segments may not necessarily be
an integral part of the casing, and gaps between each patch ring segment
may be designed to account for the thermal growth during the gas turbine
operation and/or to minimize stresses developed due to the thermal growth
in each segment. According to an example embodiment, the patch ring
segments may be individually secured to the casing by embodiments of the
invention. This may be important for at least two reasons: (1) without
securing the patch ring segments to avoid circumferential movement,
segment gaps may accumulate to create creating a larger gap, and may
create an aerodynamic concern, and (2) if instrumentation wires or probes
pass through the patch ring, and if the patch ring moves, then the probes
may bend or may shear due to the relative movement of patch ring with the
casing.

[0019] Various assemblies and parts for attaching and securing the patch
ring segments to the turbine casing will now be described with reference
to the accompanying figures according to example embodiments of the
invention. According to an example embodiment, spring-loaded pins may
reside in bore holes in the casing, and may engage in locking bores in
the patch ring sections to constrain the patch rings while averting the
risk of falling into the flow path.

[0020]FIG. 1 depicts a turbine 100 with a flow path 102. The flow path
may include buckets or blades that are attached to a rotor. The flow path
102 may be surrounded by a casing. The flow path 102 may include one or
more stages 104 for which embodiments of the invention may be applied.

[0022]FIG. 3 depicts a perspective view of an illustrative patch ring
assembly 300 according to an example embodiment of the invention. In an
example embodiment, the patch ring assembly 300 may include a patch ring
section 302, a retention pin 304, a retention pin locking bore 306, and
an optional guide slot 308.

[0023] According to an example embodiment, the turbine casing may be
modified to accept sections of a patch ring 302. In an example
embodiment, a "T" shaped channel may be machined circumferentially into
the turbine casing. A corresponding "T" shaped machined or attached
protrusion on the patch ring section may slide into the casing channel to
provide radial constraint of the patch ring sections against the casing,
while allowing the patch ring sections to slide into place. According to
an example embodiment, the patch ring sections may be constrained in the
circumferential or axial direction with the retention pin 304. According
to an example embodiment, the retention pin 304 may have a chamfer and
the patch ring 302 may have a guide slot 308 or groove on top of it so
that the pin 304 may be guided into the retention pin locking bore 306.

[0024]FIG. 4 depicts another view of the assembly 400 in an unlocked
position, according to an example embodiment of the invention. The
assembly 400 can include a patch ring segment 402, a portion of the
turbine casing 404, a retention pin 406 (shown retracted into the casing
retention pin bore 414), a compression spring 408, and a retention pin
locking bore 410. In an example embodiment, the retention pin 406 may
reside in the bore 414 within the casing 404, and may be loaded with the
spring 408 so that the retention pin 406 can engage in the retention pin
locking bore 410 within the patch ring segment 402 when the casing
retention pin bore 414 aligns with the retention pin locking bore 410.

[0025]FIG. 5 depicts another view of the assembly 500 in a locked
position. In accordance with an example embodiment of the invention, the
patch ring segment (as in 402 of FIG. 4) may be positioned so that the
retention pin 506 can engage with the retention pin locking bore 510.
According to an example embodiment, the spring 508 may provide pressure
to hold the retention pin 506 into the locking bore 510. In an example
embodiment, when the retention pin 506 is engaged in the locking bore
510, the patch ring segment may be constrained from rotating
circumferentially.

[0026]FIG. 6 depicts another view of the assembly 600, showing a
retracted retention pin 606, according to an example embodiment of the
invention. For example, a retraction tool 602 may be utilized to push the
retention pin 606 back into the casing bore so that it can clear the
patch ring segment and the patch ring segment may repositioned or
removed. In an example embodiment, the retention pin retraction bore (as
in 512 of FIG. 5) may have a smaller bore diameter than the retention pin
606 outer diameter.

[0027] An example method 700 for modifying a turbine casing will now be
described with reference to the flowchart of FIG. 7. The method 700
starts in block 702 and includes providing one or more casing retention
pin bores in the turbine casing. In block 704, method 700 includes
inserting a retention pin in the one or more casing retention pin bores.
In block 706, method 700 includes providing one or more patch ring
segments configured to be radially constrained by at least a portion of
the turbine casing and further configured to slide circumferentially in
cooperation with at least a portion of the turbine casing, wherein the
one or more patch ring segments comprise at least one retention pin
locking bore. In block 708, method 700 includes installing the one or
more patch ring segments in the turbine casing to radially constrain the
one or more patch ring segments. In block 710, method 700 includes
engaging the retention pin in the at least one retention pin locking bore
to circumferentially constrain the one or more patch ring segments to the
turbine casing. Method 700 ends after block 710.

[0028] In example embodiments, engaging the retention pin (304) in the at
least one retention pin locking bore (510) includes engaging at least a
portion of the retention pin (304) in at least one of the one or more
casing retention pin bores (414), and further engaging at least a portion
of the retention pin (304) in the at least one retention pin locking bore
(510) when the one or more casing retention pin bores (414) are
circumferentially aligned with the at least one retention pin locking
bore (510).

[0029] Example embodiments include inserting a spring (408) in the one or
more casing retention pin bores (414), wherein the spring (408) provides
force for engaging the retention pin (304) in the at least one retention
pin locking bore (410). According to example embodiments, providing one
or more casing retention pin bores (414) in the turbine casing (404)
includes providing one or more radial bores in the turbine casing (404).
In example embodiments, installing the one or more patch ring segments
(402) in the turbine casing (404) includes installing the one or more
patch ring segments (402) in a flow path stage (204) associated with the
turbine. In example embodiments, providing one or more patch ring
segments (402) further includes providing a guide slot (308) in the one
or more patch ring segments (402) for guiding the retention pin (304)
into the at least one retention pin locking bore (410). According to
example embodiments, providing one or more patch ring segments (402)
further includes providing a retention pin retraction bore (512) for
disengaging the retention pin (304) from the least one retention pin
locking bore (410), wherein the retention pin retraction bore (512)
includes a diameter smaller than the diameter of the retention pin (304).

[0030] Example embodiments of the invention include system and an
apparatus. The system can include a gas turbine (100) that includes a
flow path stage casing (404). The system and the apparatus can include an
assembly for repairing the casing (404). The assembly can include one or
more casing retention pin bores (414) in the casing (404); a retention
pin (304) in the one or more casing retention pin bores (414); one or
more patch ring segments (402) configured to be radially constrained by
at least a portion of the casing (404) and further configured to slide
circumferentially during assembly or disassembly in cooperation with at
least a portion of the turbine casing (404), wherein the one or more
patch ring segments include at least one retention pin locking bore
(510), and wherein the retention pin (304) engages with the at least one
retention pin locking bore (510) to circumferentially constrain the one
or more patch ring segments (402) to the casing (404).

[0031] According to example embodiments, the retention pin is operable to
engage with at least a portion of one of the one or more casing retention
pin bores (414), and wherein the retention pin is further operable to
engage with at least a portion of the at least one retention pin locking
bore (510) when the one or more casing retention pin bores (414) are
circumferentially aligned with the at least one retention pin locking
bore (510).

[0032] According to example embodiments, the system and/or the apparatus
can include a spring (408) positioned in the one or more casing retention
pin bores (414), wherein the spring (408) provides force for engaging the
retention pin (304) in the at least one retention pin locking bore (410).
In an example embodiment, the one or more casing retention pin bores
(414) include radial bores in the casing (404). In an example embodiment,
the one or more patch ring segments (402) further include a guide slot
(308) for guiding the retention pin (304) into the at least one retention
pin locking bore (410). In example embodiments, the one or more patch
ring segments (402) further include a retention pin retraction bore (512)
for disengaging the retention pin (304) from the least one retention pin
locking bore (410), wherein the retention pin retraction bore (512)
includes a diameter smaller than the diameter of the retention pin (304).

[0033] According to example embodiments, certain technical effects can be
provided, such as creating certain systems, methods, and apparatus that
provide securing patch ring segments to a turbine casing while avoiding
the use of screws or other fastening devices that could fall in the flow
path.

[0034] In example embodiments of the invention, the assembly 300, 400,
500, and 600 may include any number of hardware components to facilitate
any of the operations described by the methods described herein, such as
700 in FIG. 7.

[0035] While certain embodiments of the invention have been described in
connection with what is presently considered to be the most practical and
various embodiments, it is to be understood that the invention is not to
be limited to the disclosed embodiments, but on the contrary, is intended
to cover various modifications and equivalent arrangements included
within the scope of the appended claims. Although specific terms are
employed herein, they are used in a generic and descriptive sense only
and not for purposes of limitation.

[0036] This written description uses examples to disclose certain
embodiments of the invention, including the best mode, and also to enable
any person skilled in the art to practice certain embodiments of the
invention, including making and using any devices or systems and
performing any incorporated methods. The patentable scope of certain
embodiments of the invention is defined in the claims, and may include
other examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if they have
structural elements that do not differ from the literal language of the
claims, or if they include equivalent structural elements with
insubstantial differences from the literal language of the claims.